GY-63_MS5611/libraries/DHTlib/dht.cpp
2017-03-06 21:10:50 +01:00

201 lines
5.6 KiB
C++

//
// FILE: dht.cpp
// AUTHOR: Rob Tillaart
// VERSION: 0.1.22
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
// URL: http://arduino.cc/playground/Main/DHTLib
//
// HISTORY:
// 0.1.22 undo delayMicroseconds() for wakeups larger than 8
// 0.1.21 replace delay with delayMicroseconds() + small fix
// 0.1.20 Reduce footprint by using uint8_t as error codes. (thanks to chaveiro)
// 0.1.19 masking error for DHT11 - FIXED (thanks Richard for noticing)
// 0.1.18 version 1.16/17 broke the DHT11 - FIXED
// 0.1.17 replaced micros() with adaptive loopcount
// removed DHTLIB_INVALID_VALUE
// added DHTLIB_ERROR_CONNECT
// added DHTLIB_ERROR_ACK_L DHTLIB_ERROR_ACK_H
// 0.1.16 masking unused bits (less errors); refactored bits[]
// 0.1.15 reduced # micros calls 2->1 in inner loop.
// 0.1.14 replace digital read with faster (~3x) code => more robust low MHz machines.
//
// 0.1.13 fix negative temperature
// 0.1.12 support DHT33 and DHT44 initial version
// 0.1.11 renamed DHTLIB_TIMEOUT
// 0.1.10 optimized faster WAKEUP + TIMEOUT
// 0.1.09 optimize size: timeout check + use of mask
// 0.1.08 added formula for timeout based upon clockspeed
// 0.1.07 added support for DHT21
// 0.1.06 minimize footprint (2012-12-27)
// 0.1.05 fixed negative temperature bug (thanks to Roseman)
// 0.1.04 improved readability of code using DHTLIB_OK in code
// 0.1.03 added error values for temp and humidity when read failed
// 0.1.02 added error codes
// 0.1.01 added support for Arduino 1.0, fixed typos (31/12/2011)
// 0.1.00 by Rob Tillaart (01/04/2011)
//
// inspired by DHT11 library
//
// Released to the public domain
//
#include "dht.h"
/////////////////////////////////////////////////////
//
// PUBLIC
//
int8_t dht::read11(uint8_t pin)
{
// READ VALUES
int8_t result = _readSensor(pin, DHTLIB_DHT11_WAKEUP, DHTLIB_DHT11_LEADING_ZEROS);
// these bits are always zero, masking them reduces errors.
bits[0] &= 0x7F;
bits[2] &= 0x7F;
// CONVERT AND STORE
humidity = bits[0]; // bits[1] == 0;
temperature = bits[2]; // bits[3] == 0;
// TEST CHECKSUM
// bits[1] && bits[3] both 0
uint8_t sum = bits[0] + bits[2];
if (bits[4] != sum)
{
return DHTLIB_ERROR_CHECKSUM;
}
return result;
}
int8_t dht::read(uint8_t pin)
{
// READ VALUES
int8_t result = _readSensor(pin, DHTLIB_DHT_WAKEUP, DHTLIB_DHT_LEADING_ZEROS);
// these bits are always zero, masking them reduces errors.
bits[0] &= 0x03;
bits[2] &= 0x83;
// CONVERT AND STORE
humidity = (bits[0]*256 + bits[1]) * 0.1;
temperature = ((bits[2] & 0x7F)*256 + bits[3]) * 0.1;
if (bits[2] & 0x80) // negative temperature
{
temperature = -temperature;
}
// TEST CHECKSUM
uint8_t sum = bits[0] + bits[1] + bits[2] + bits[3];
if (bits[4] != sum)
{
return DHTLIB_ERROR_CHECKSUM;
}
return result;
}
/////////////////////////////////////////////////////
//
// PRIVATE
//
int8_t dht::_readSensor(uint8_t pin, uint8_t wakeupDelay, uint8_t leadingZeroBits)
{
// INIT BUFFERVAR TO RECEIVE DATA
uint8_t mask = 128;
uint8_t idx = 0;
uint8_t data = 0;
uint8_t state = LOW;
uint8_t pstate = LOW;
uint16_t zeroLoop = DHTLIB_TIMEOUT;
uint16_t delta = 0;
leadingZeroBits = 40 - leadingZeroBits; // reverse counting...
// replace digitalRead() with Direct Port Reads.
// reduces footprint ~100 bytes => portability issue?
// direct port read is about 3x faster
uint8_t bit = digitalPinToBitMask(pin);
uint8_t port = digitalPinToPort(pin);
volatile uint8_t *PIR = portInputRegister(port);
// REQUEST SAMPLE
pinMode(pin, OUTPUT);
digitalWrite(pin, LOW); // T-be
if (wakeupDelay > 8) delay(wakeupDelay);
else delayMicroseconds(wakeupDelay * 1000UL);
digitalWrite(pin, HIGH); // T-go
pinMode(pin, INPUT);
uint16_t loopCount = DHTLIB_TIMEOUT * 2; // 200uSec max
// while(digitalRead(pin) == HIGH)
while ((*PIR & bit) != LOW )
{
if (--loopCount == 0) return DHTLIB_ERROR_CONNECT;
}
// GET ACKNOWLEDGE or TIMEOUT
loopCount = DHTLIB_TIMEOUT;
// while(digitalRead(pin) == LOW)
while ((*PIR & bit) == LOW ) // T-rel
{
if (--loopCount == 0) return DHTLIB_ERROR_ACK_L;
}
loopCount = DHTLIB_TIMEOUT;
// while(digitalRead(pin) == HIGH)
while ((*PIR & bit) != LOW ) // T-reh
{
if (--loopCount == 0) return DHTLIB_ERROR_ACK_H;
}
loopCount = DHTLIB_TIMEOUT;
// READ THE OUTPUT - 40 BITS => 5 BYTES
for (uint8_t i = 40; i != 0; )
{
// WAIT FOR FALLING EDGE
state = (*PIR & bit);
if (state == LOW && pstate != LOW)
{
if (i > leadingZeroBits) // DHT22 first 6 bits are all zero !! DHT11 only 1
{
zeroLoop = min(zeroLoop, loopCount);
delta = (DHTLIB_TIMEOUT - zeroLoop)/4;
}
else if ( loopCount <= (zeroLoop - delta) ) // long -> one
{
data |= mask;
}
mask >>= 1;
if (mask == 0) // next byte
{
mask = 128;
bits[idx] = data;
idx++;
data = 0;
}
// next bit
--i;
// reset timeout flag
loopCount = DHTLIB_TIMEOUT;
}
pstate = state;
// Check timeout
if (--loopCount == 0)
{
return DHTLIB_ERROR_TIMEOUT;
}
}
pinMode(pin, OUTPUT);
digitalWrite(pin, HIGH);
return DHTLIB_OK;
}
//
// END OF FILE
//